Public Test Realm is a great name for a patch preview server. It sounds grand and democratic, like the ornate forum of a philosophically minded republic. It's much better than what I'd have called it: probably Alpha Hovel or Beta Bin. Starcraft 2: Heart of the Swarm's own Trial Toilet has been filled with the first drops of the upcoming patch 2.1, giving players an early preview of a reworked custom map system, an event calendar for clans and groups, and a set of classic soundtracks, optionally enabling the tunes of StarCraft and Brood War into non-campaign matches.
"Extension mods will help streamline the mod creation process for map developers and allow players to more easily find and play their favorite mods," Blizzard write of their reworked mod feature. It allows players to apply the parameters of a mod to any map in the custom game list. As such, custom map players will no longer need to check if the mod they want is available for their preferred maps, instead being able to apply the Extension Mod to whichever maps they like.
Other features include a new Events tab, allowing clans and groups to create a schedule; the aforementioned classic soundtracks, available as an option in the settings menu; and new rules for lobbies, that will kick and reassign the host should they go idle.
To try it out, open the Battle.net launcher , and change your region to PTR: Heart of the Swarm.